Internal Rotation IV. The Optical Activity and Isomerization Energy of the Rotational Isomers of D-Secondary Butyl Alcohol

Abstract

The specific rotation of secondary butyl alcohol was measured in dilute solutions of cyclohexane at intervals of 5° between 20°C and 70°C inclusive. After corrections for solvent effect and change of refractive index with temperature had been made there remained a definite temperature dependence of the rotivity. Interpretation of the results on the basis of three optically active rotational isomers (two of equal energy and the third less stable) gave the rotivity of the third isomer as −21° and the sum of the other two as +21°. The heat of isomerization was found to be 803 cal. per mole. The concentrations of the three rotational isomers at 20° are calculated as 42.3 percent, 42.3 percent, and 15.3 percent.

Chiroptical Properties of Organic Radical Cations. The Electronic and Vibrational Circular Dichroism Spectra of α-Tocopherol Derivatives and Sterically Hindered Chiral Hydroquinone Ethers

“…The absolute configuration of 2-butanol is of particular importance in stereochemistry, because a large number of chiral compounds are related to this simple chirogenic group. Thus, the conformational preference of 2-butanol is also a crucial recent topic, which has been studied carefully by using VT-polarimetry, NMR spectroscopy, Raman spectra combined with MM3 calculations and VCD spectroscopy combined with DFT calculations . These experiments indicate that the T conformer, possessing the anti C−C−C*-C bond, is lowest in energy, but the other two conformers (i.e., gauche plus ( G + ) and minus ( G - )) are also populated in the ratio T : G + : G - = ca.…”